Initiator or catalyst systems for polymerizations often exhibit highly variable and poorly controllable or reproducible activity since the typically extremely low concentration of active centers is strongly influenced by preparation conditions and the presence of trace components.
The assessment of a initiator or catalyst systems typically require intense testing since established analytic methods suitable for online monitoring of the activity of initiators or catalysts are currently not available.
Real-time monitoring of monomer consumption and polymer formation for example via ATR-IR or calorimetric measurements is known from Storey, R. F.; Donnalley, A. B.; Maggio, T. L. Macromolecules 1998, 31, 1523 and A. Ledwith, E. Lockett, D. C. Sherrington, Polymer 1975, 16, 31. However, the contribution and quality of the initiator activity and their distinction from other factors that also may influence polymerization kinetics was not measured.
In X. Xu, Y. Wu, Y. Qiu, C. Dong, G. y. Wu, H. Wang, Eur. Polym. J. 2006, 42, 2791 and L. Balogh, L. Fabián, I. Majoros, T. Kelen, Polym. Bull. 1990, 23, 75 conductivity measurements have been used to determine ion concentrations and degree of dissociation in initiator solutions.
In G. Heublein, J. Macromol. Sci.-Chem. 1985, A22, 1277 and R. Metava, C. Konstantinov, V. Kaibanov, J. Polym. Sci. Part A, Polym. Chem. 1970, 8, 3563 attempts are disclosed to link initiator characteristics to catalytic activity.
It is further known from EP 0 948 761 A to control the properties of a halobutyl rubber product by using variable process parameters, in particular Mooney viscosity and polymer molecular weight distribution as process control parameters. The process is performed using an in situ measurement system that does not require the removal of any sample material from the process and which comprises inter alia a Fourier Transform Near Infrared (FTNIR) spectrometer. However, EP 0 948 761 A does not disclose a manufacturing process for polymers which uses the activity of a catalyst or a initiator employed in a polymerization process as process control parameter.
Therefore, there was still a need for a process which allows to determine the activity before using the initiator or catalyst in a continuous or batch polymerization reaction and in particular to control the amount of catalyst or initiator employed in said polymerization process by using the activity as process control parameter.